This invention culminates the endeavor to design and produce a highly marketable soil moisture indicator. All previous patents covered designs such as those requiring a large battery (e.g. 9 volts) that was being continuously drained at high power requirements and thus was not designed with continuous soil moisture monitoring in mind; the units had to be first acquired with forethought, turned-on and placed into soil for a reading. Even if these units didn't have this problem, constant unidirectional current through probes such as in prior art patents would very quickly electrolysize, preventing them from remaining in soil. Even further, if this were no problem, and previous patents had incorporated alternating short duration and low frequency on the probes, as does this invention, their lack of probe plating with rhodium, chromium or some such substance to prevent quiescent corrosion is another drawback that prevents continuous in-soil resident automatic moisture monitoring and indication.
For example, one prior art patent employs bi-metallic cylindrical probes, therein described, which, if left in soil, would corrode and electrolyze, not to mention the fact of its cumbersome cord from probe to meter case assembly.
Advantages of the invention over the prior art include, small size due to integrated circuit DC/DC converter; small battery requirement due to (a) slow repetition indication occurring only during dry soil periods, (b) integrated circuit employing all transistor and function operations; resident soil operation capability due to moisture resistant conductors on printed circuit board probes and slow repetition, fast duration, alternating probe voltage pulsing; a calibrated user dial to adjust for dry indication level; a hysterysis dual trip level wherein the dry level is user adjustable and the wetness level is set, and must be reached to shut off beep/flash indication. This is in direct contrast to prior art devices which are nonautomatic in nature, requiring forethought in usage, and thus not being a plant soil fail-safe system. These prior art devices also do not have a calibrated-numbered user adjustment potentiometer to adjust the unit for different plants' soil minimum wetness levels (except for a scientific moisture content meter in one patent which incorporates a variable extremely well calibrated dial, but includes a front-end current to logarithm voltage converter and is for scientific use, and thus is a high current device not suitable for domestic and commercial usage). The prior art devices also do not include a single LED to flash on during sampling time when prior samples measured dry soil; a piezoceramic beeper to beep in unison with LED flash during dry indication; an out-of-soil automatic shut-off sensing circuit to enable a "too dry to possibly be a soil" condition for packaging and shelf life, and for plant-to-plant insertion and dryness monitoring.